added basic drag and drop of selected text

TODO: use system DnD events and add drag image

2 files changed, 104 insertions, 0 deletions

diff --git a/README.md b/README.md
index 4ca8550..3f26d59 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,7 @@ Plugin | Description
 [`copyfilelocation`](plugins/copyfilelocation.lua?raw=1) | Copy file location to clipboard
 [`datetimestamps`](plugins/datetimestamps.lua?raw=1) | Insert date-, time- and date-time-stamps
 [`detectindent`](plugins/detectindent.lua?raw=1) | Automatically detects and uses the indentation size and tab type of a loaded file
+[`draganddropselectedtext`](plugins/draganddropselectedtext.lua?raw=1) | Provides basic drag and drop of selected text (in same document)
 [`drawwhitespace`](plugins/drawwhitespace.lua?raw=1) | Draws tabs and spaces *([screenshot](https://user-images.githubusercontent.com/3920290/80573013-22ae5800-89f7-11ea-9895-6362a1c0abc7.png))*
 [`eval`](plugins/eval.lua?raw=1) | Replaces selected Lua code with its evaluated result
 [`exec`](plugins/exec.lua?raw=1) | Runs selected text through shell command and replaces with result
diff --git a/plugins/draganddropselectedtext.lua b/plugins/draganddropselectedtext.lua
new file mode 100644
index 0000000..984f209
--- /dev/null
+++ b/plugins/draganddropselectedtext.lua
@@ -0,0 +1,103 @@
+--[[
+    draganddropselectedtext.lua
+    provides basic drag and drop of selected text (in same document)
+    version: 20200626_013631
+    originally by SwissalpS
+
+    TODO: use OS drag and drop events
+    TODO: change mouse cursor when duplicating
+    TODO: add dragging image
+--]]
+local DocView = require "core.docview"
+local core = require "core"
+local keymap = require "core.keymap"
+
+-- helper function for on_mouse_pressed to determine if mouse down is in selection
+-- iLine is line number where mouse down happened
+-- iCol is column where mouse down happened
+-- iSelLine1 is line number where selection starts
+-- iSelCol1 is column where selection starts
+-- iSelLine2 is line number where selection ends
+-- iSelCol2 is column where selection ends
+local function isInSelection(iLine, iCol, iSelLine1, iSelCol1, iSelLine2, iSelCol2)
+    if iLine < iSelLine1 then return false end
+    if iLine > iSelLine2 then return false end
+    if (iLine == iSelLine1) and (iCol < iSelCol1) then return false end
+    if (iLine == iSelLine2) and (iCol > iSelCol2) then return false end
+    return true
+end -- isInSelection
+
+-- override DocView:on_mouse_moved
+local on_mouse_moved = DocView.on_mouse_moved
+function DocView:on_mouse_moved(x, y, ...)
+
+    -- make sure we only act if previously on_mouse_pressed was in selection
+    if self.bClickedIntoSelection then
+
+        -- check for modifier to duplicate
+        -- (may want to set a flag as this only needs to be done once)
+        -- TODO: make image to drag with and/or hand over to OS dnd event
+        if not keymap.modkeys['ctrl'] then
+            -- TODO: maybe check if moved at all and only delete then or
+            -- as some editors do, only when dropped. I do like it going
+            -- instantly as that reduces the travel-distance.
+            self.doc:delete_to(0)
+            --self.cursor = 'arrowWithPlus'
+        end
+        -- calculate line and column for current mouse position
+        local iLine, iCol = self:resolve_screen_position(x, y)
+        -- move text cursor
+        self.doc:set_selection(iLine, iCol)
+        -- update scroll position
+        self:scroll_to_line(iLine, true)
+
+    end -- if previously clicked into selection
+
+    -- hand off to 'old' on_mouse_moved()
+    return on_mouse_moved(self, x, y, ...)
+
+end -- DocView:on_mouse_moved
+
+-- override DocView:on_mouse_pressed
+local on_mouse_pressed = DocView.on_mouse_pressed
+function DocView:on_mouse_pressed(button, x, y, clicks)
+
+    -- no need to proceed if not left button or has no selection
+    if ('left' ~= button)
+      or not self.doc:has_selection() then
+        return on_mouse_pressed(self, button, x, y, clicks)
+    end
+    -- convert pixel coordinates to line and column coordinates
+    local iLine, iCol = self:resolve_screen_position(x, y)
+    -- get selection coordinates
+    local iSelLine1, iSelCol1, iSelLine2, iSelCol2 = self.doc:get_selection(true)
+    -- set flag for on_mouse_released and on_mouse_moved() methods to detect dragging
+    self.bClickedIntoSelection = isInSelection(iLine, iCol, iSelLine1, iSelCol1,
+                                               iSelLine2, iSelCol2)
+    if self.bClickedIntoSelection then
+        -- stash selection for inserting later
+        self.sDraggedText = self.doc:get_text(self.doc:get_selection())
+    else
+        -- let 'old' on_mouse_pressed() do whatever it needs to do
+        on_mouse_pressed(self, button, x, y, clicks)
+    end
+
+end -- DocView:on_mouse_pressed
+
+-- override DocView:on_mouse_released()
+local on_mouse_released = DocView.on_mouse_released
+function DocView:on_mouse_released(button)
+
+    if self.bClickedIntoSelection then
+        -- insert stashed selected text at current position
+        self.doc:text_input(self.sDraggedText)
+        -- unset stash and flag(s) TODO:
+        self.sDraggedText = ''
+        self.bClickedIntoSelection = nil
+    end
+
+    -- hand over to old handler
+    on_mouse_released(self, button)
+
+end -- DocView:on_mouse_released
+